U.S. Pat. No. 3,965,143 generally describes compounds of the formula ##STR2## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.6 and R.sub.7 can be hydrogen or a lower alkyl radical, R.sub.5 can be hydrogen or a lower alkanoyl, tetrahydrofuranyl, tetrahydropyran-2-yl, tri(-lower alkyl)silyl or lower alkyl radical, X is a carbonyl, hydroxymethylene or (lower alkanoyl) oxymethylene radical, V is a methylene, hydroxymethylene (lower alkanoyl) oxymethylene, tetrahydrofuranyloxymethylene, tetrahydropyran-2-yloxymethylene or tri-(lower alkyl)silyloxymethylene radical, Y is an ethylene, cis vinylene or trans-vinylene group, Z is an ethylene, cis vinylene, trans-vinylene or ethynylene radical, the wavy lines denote the alternative R and S stereochemical configurations, the dotted line indicates an optional double bond, m is an integer greater than 2 and less than 5 and R.sub.8 is an alkyl group containing 3-5 carbon atoms or cycloalkyl group containing 5-7 carbon atoms. British Pat. No. 1,492,426 describes compounds of the structural formula. ##STR3## wherein R.sub.1, R.sub.2 and R.sub.3 are hydrogen or an alkyl radical containing from 1 to 7 carbon atoms; R.sub.4 is an alkyl radical containing from 1 to 7 carbon atoms; R.sub.5 is hydrogen, an alkyl radical containing from 1 to 7 carbon atoms or an alkanoyl radical containing from 1 to 7 carbon atoms; R.sub.6 is an alkyl radical containing from 2 to 4 carbon atoms or a cycloalkyl radical containing from 5 to 7 carbon atoms; X is carbonyl or hydroxymethylene; V is methylene, hydroxymethylene or alkanoyloxymethylene wherein the alkanoyl radical contains from 1 to 7 carbon atoms; or when X is carbonyl; V may also be a radical of the formula ##STR4## in which the bond represented by the dotted line in the general formula is present; Y is ethylene or vinylene; Y' is vinylene, ethynylene or the group ##STR5## wherein n is 0 to 1 and R.sub.7 and R.sub.8 are hydrogen or an alkyl radical containing from 1 to 7 carbon atoms; Z is ethylene, vinylene or ethynylene; and the wavy lines represent the alternative A or B stereochemical configuration or the epimeric mixture: U.S. Pat. No. 4,499,296 describes compounds of the formula. ##STR6## wherein R'" represents hydroxymethyl, hydroxyacetyl or --CO.sub.2 R"" wherein R"" represents hydrogen or lower alkyl containing 1 to 6 carbon atoms; R' represents lower alkyl containing 1 to 6 carbon atoms, vinyl or ethynyl; R" represents cycloalkyl containing 3 to 5 carbon atoms; and the wavy line represents optional R, S stereochemistry. European Patent Application No. 84 113676.5 describes prostaglandins of the formula I ##STR7## wherein X represents cis or trans --CH.dbd.CH--, --C.tbd.C--, methylene or ethylene; R.sub.1 represents a cycloalkyl group of the formula ##STR8## where m is 1 to 3 inclusive; R.sub.2 represents hydrogen or lower alkyl with the proviso that the sum of the carbon atoms in X and R.sub.1 is 7 or less.
R' represents lower alkyl containing 1 to 6 carbon atoms, vinyl or ethynyl; and R'" is as defined above.